1. Field of the Invention
The present invention relates to a thin finite linear motion rolling guide unit and, more particularly, to a unit which can be miniaturized as a whole and can maintain a high linear motion rolling accuracy for a long time by assembling a belt or a similar mechanism for preventing a positional deviation of a holder of the rolling guide unit.
2. Description of the Prior Art
A conventional technique of an apparatus for preventing a positional deviation of a holder using a belt has been disclosed in, for instance, Japanese Patent Application No. 56-113824.
According to such a technique, a holder is extended outwardly in the sliding direction of a track member, pulleys are provided in the extension edge portion, and a belt whose both ends are fixed is come into contact with upper and lower track members, thereby restricting the motion of the holder to 1/2 of that of a rolling guide unit and also accomplishing the dust proofing of the rolling guide unit.
However, since the pulleys are formed on the outside of the track member, there is a problem such that the whole rolling guide unit becomes longer. In addition, the whole holder becomes long and the weight of the pulleys is loaded to both ends of the holder, so that there occur problems such that the holder is easily deformed and a partial abnormal abrasion is caused and the slide resistance increases. There is a drawback such that the life of the rolling guide unit becomes short due to the deviation preventing apparatus.
Further, since two pulleys are formed at front and back positions, there is a drawback such that the number of parts increases and the costs are high.
As mentioned above, in the well-known construction, many problems are not solved yet. According to the invention, in order to solve such conventional drawbacks, one pulley or one pin to turn the direction of a belt or a rope is attached in the central portion of the sliding direction of a holder and the belt or rope is wrapped around the pulley or pin from both ends, thereby restricting a movement amount of the holder to 1/2 of a movement amount of a table.
Since the structure of the invention is simpler than that of the conventional technique, the construction of the invention is optimum to an apparatus for preventing a positional deviation of a holder of a relatively small thin linear motion rolling guide unit.